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Professor Alistair Duffy

Job: Professor of Electromagnetics, Associate Dean of Research and Innovation

Faculty: Computing, Engineering and Media

School/department: School of Engineering and Sustainable Development

Research group(s): Advanced Manufacturing Processes and Mechatronics Centre (AMPMC), Centre for Electronic and Communications Engineering (CECE)

Address: ÐßÐßÊÓƵ, The Gateway, Leicester, LE1 9BH UK

T: +44 (0)116 257 7056

E: apd@dmu.ac.uk

W:

 

Personal profile

Alistair Duffy is Professor of Electromagnetics, and Associate Dean of Research and Innovation in the Faculty of Technology at ÐßÐßÊÓƵ, Leicester, UK. He received the Bachelor’s degree in Electrical and Electronic Engineering and an MEng degree from University College, Cardiff, UK, in 1988 and 1989, respectively. After receiving the Master’s degree, he joined the research group of Professors Christopoulos and Benson at Nottingham University. There he worked on experimental validation of numerical modelling and received his PhD in 1993. Dr Duffy completed his professional education in 2004 with an MBA from Open University, UK. He is widely published, with over 200 technical papers and articles, mostly on his research interests of validation of computational electromagnetics; physical layer components, particularly communications cabling, and electromagnetic compatibility testing. 

Dr Duffy has contributed to many successful conferences through refereeing functions or organising committee responsibilities. He currently serves on the Board of Directors of the International Wire and Cable Symposium, which attracts approximately 1,000 delegates annually. He is an Associate Editor for the IEEE Transactions on EMC and an Associate Editor of the ACES Journal. Other professional activities include standards body work in the UK (British Standards Institute) and in the IEEE, where he is currently Chair of the EMC Society's Standards Development and Education Committee (SDECom). He is also the Society’s Global EMC Symposium Coordinator. From 2008 to 2009 he served the IEEE EMC Society as a Distinguished Lecturer. In 2015, Dr Duffy was elected to the grade of IEEE Fellow for the development of validation methods in computational electromagnetics.

Dr Duffy was a Series Editor for undergraduate textbooks published by Butterworth-Heinemann (now part of Elsevier) and SciTech Publishing (now part of the IET) on EMC. He has supervised 20 PhD students during his career.

Publications and outputs


  • dc.title: Design, simulation, and fabrication of a double annular ring microstrip antenna based on gaps with multiband feature dc.contributor.author: Al-Tumah, Wa'il A. Godaymi; Shaaban, Raed M.; Duffy, A. P. dc.description.abstract: A novel double annular-ring microstrip antenna, split into six sectors, is proposed to achieve multiband operation with high gain and impedance bandwidth. The gaps on the driven and parasitic patches excite resonant frequencies that are located in the Ku-, K-, and Ka-bands thus making the antenna capable of these multiband applications. The present design is numerically and experimentally investigated. This investigation indicates that the suggested antenna achieves four operating bands, with impedance bandwidths of 1.72 GHz (12.16–13.88 GHz), 2.04 GHz (19.28–21.32 GHz), 1.54 GHz (24.04–25.58 GHz), and 1.97 GHz (27.37–29.34 GHz) which correspond to the resonant frequencies of 13.10 GHz, 20.72 GHz, 25.00 GHz, and 28.85 GHz, respectively. Also, the new design achieves good values of gain (6.11–8.31) dB and a return loss of between −16.14 dB and −21.52 dB. The commercial tool Ansoft high frequency structure simulator is used to simulate the designed antennas and it compared with the obtained measurement data. The comparison shows close agreement between the simulations and measurements. dc.description: open access article

  • dc.title: Improvements proposed to noisy-OR derivatives for multi-causal analysis: A case study of simultaneous electromagnetic disturbances dc.contributor.author: Devaraj, Lokesh; Khan, Qazi Mashaal; Ruddle, Alastair R.; Duffy, A. P.; Perdriau, Richard; Koohestani, Mohsen dc.description.abstract: In multi-causal analysis, the independence of causal influence (ICI) assumed by the noisy-OR (NOR) model can be used to predict the probability of the effect when several causes are present simultaneously, and to identify (when it fails) inter-causal dependence (ICD) between them. The latter is possible only if the probability of observing the multi-causal effect is available for comparison with a corresponding NOR estimate. Using electromagnetic interference in an integrated circuit as a case study, the data corresponding to the probabilities of observing failures (effect) due to the injection of individual (single cause) and simultaneous electromagnetic disturbances having different frequencies (multiple causes) were collected. This data is initially used to evaluate the NOR model and its existing derivatives, which have been proposed to reduce the error in predictions for higher-order multi-causal interactions that make use of the available information on lower-order interactions. Then, to address the identified limitations of the NOR and its existing derivatives, a new deterministic model called Super-NOR is proposed, which is based on correction factors estimated from the available ICD information.

  • dc.title: The Effect of the Ring Mains Units for On-line Partial Discharge Location with Time Reversal in Medium Voltage Networks dc.contributor.author: Ragusa, Antonella; Wouters, Peter A. A. F.; Sasse, Hugh; Duffy, A. P. dc.description.abstract: The performance of a new on-line partial discharge (PD) location method based on the Electromagnetic Time Reversal (EMTR) theory and the Transmission Line Matrix (TLM) method are investigated for characterization of Medium-Voltage (MV) networks. The generated distortion of the PD signal during its propagation along a network with realistically modelled components is reproduced in simulation and the effectiveness of the EMTR-based method to localise the PD source is analyzed. In particular, the effects of the ring main units (RMUs), that behave as a complex impedance, the variation with frequency of the MV cable impedance and the reflection patterns, due to impedance mismatches, are considered and investigated. Simulation results are given showing the performance of the EMTR method in two different networks configurations: the former one with a RMU at the end of a MV cable and the latter one with a second MV cable connected to the RMU of the first configuration having a distribution transformer at its far end. The results show that the EMTR method is able, with only a single observation point, to localise PDs also in the presence of RMU with a relative error, with respect to the line length, of approximately 1%. dc.description: open access article

  • dc.title: Electromagnetic time reversal for online partial discharge location in power cables: Influence of interfering reflections from grid components dc.contributor.author: Ragusa, Antonella; Wouters, Peter A. A. F.; Sasse, Hugh; Duffy, A. P.; Rachidi, Farhad; Rubinstein, Marcos dc.description.abstract: In online single-sided partial discharge (PD) location, the measured PD reflection patterns are affected by the characteristics of all the components of the associated power network. This paper analyses the performance of a PD location method based on electromagnetic time reversal (EMTR) theory, when interfering reflections contribute to the transient signals emitted by the PD event. The topology analysed is formed from a ring main unit (RMU) in a medium voltage grid with mixed cross-linked polyethylene and paper-insulated lead-covered (PILC) cable sections. The PD reflection patterns, observed at the RMU, are disturbed by the reflections coming from the impedance discontinuities of the circuit and by the reflections coming from the cable ends of the PILC cables connected to the RMU. The simulated configuration is chosen such that classical location techniques tend to fail due to overlapping peaks and other signal distortion. This is because the classic techniques are based on identifying individual reflection peaks from which the PD source can be determined via differences in time of arrival. The numerical investigation shows that the accuracy of the EMTR-based location method is robust against these effects, achieving a PD localisation with an error less than the 0.1%. The results also show that the EMTR-based method can localise PDs using a PD monitoring point located somewhere along the network and not necessarily at the line termination. dc.description: open access article

  • dc.title: Determination of the Physical Integrity of Ethernet Cables by Obtaining their Transmission Line Parameters from Measured Impedance Profiles dc.contributor.author: Ogundapo, Olusegun; Duffy, A. P. dc.description.abstract: A method of determining the physical integrity of Ethernet cables by obtaining their transmission line parameters (resistance, inductance, capacitance, and conductance) from their measured impedance profiles are presented. The transmission line parameters were extracted across the cable lengths rather than frequencies used in most research. The method can be used to examine the physical integrity of Ethernet cables before their deployment. The study of the physical integrity of Ethernet cables is very important because, in typical installations, cables can be manipulated in the form of repeated coiling and uncoiling. The installation handling stress can adversely affect the signal integrity especially if they are substandard Ethernet cables. In this paper, four Ethernet cables were subjected to three coiling and uncoiling tests to represent installation handling stress. The impedance profiles of the four cables across their lengths were measured for the three handling stress test conducted. The computation of the transmission line parameters of the Ethernet cables using measured impedance profiles was implemented with the aid of Matrix Laboratory (MATLAB). The outcome of the research showed that the method presented will be very useful to cable installers and contractors in making objective decisions in the choice of cables for deployment. dc.description: open access article

  • dc.title: Step Frequency TR-MUSIC for Soft Fault Detection and Location in Coaxial Cable dc.contributor.author: He, Xin; Wang, Lixin; Yang, Dazhi; Chang, Kaixing; Duffy, A. P.; Zhang, Gang dc.description.abstract: Soft faults in cables may trigger short circuits and open circuits in time, in that, they ought to be detected and thus eliminated at an earliest possible stage, as to ensure safe and stable operation of the cables. A method called the time-reversal multiple signal classification (TR-MUSIC) had been proposed in the literature, which has been demonstrated to be an effective technique for locating soft faults in cables, owing to its high resolution and excellent noise robustness. However, traditional TR-MUSIC relies on a vector network analyzer for measuring the scattering matrix of cables, which adds cost and complexity to its implementation. In this regard, a new way of acquiring the desired scattering parameters is herein proposed. An arbitrary function generator is used to inject incident signals into the cable under test, and an oscilloscope is used to collect the reflected signals. After post-processing, the phase of scattering parameters can be obtained. There's another key issue in the image of the detection results, ghost traces caused by the periodicity of Green's function severely impact the vision saliency of the actual fault location, which limits the performance of the fault location. A step frequency variant of TR-MUSIC has been proposed, therefore, to mitigate ghost traces. Experimental results show that the fault location error of the proposed approach is smaller than 0.33% for a 51-m long coaxial cable. Moreover, in the case of introducing noise, the proposed approach can operate in situations with signal-to-noise ratios as low as dB. dc.description: The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.

  • dc.title: Electromagnetic Design and Analysis in Electrical Power Conversion and Usage dc.contributor.author: Duffy, A. P.; Zhang, Gang dc.description: open access article

  • dc.title: Thermal Effects on Crosstalk of Multiconductor PVC Cables and Estimation of Thermal Accelerating Ratios dc.contributor.author: Zhang, Gang; Chen, Xiao; Yang, Dazhi; Duffy, A. P.; Li, Ming; Wang, Lixin dc.description.abstract: This paper is concerned with how crosstalk amplitudes of multi-conductor PVC cables vary with heating temperatures and time to determine thermal effects on the cables in realistic conditions, and thus proposes a method to estimate aging rates and acceler-ating ratios with respect to the variation of crosstalk amplitudes. First, the mechanism of thermal effects on crosstalk of multicon-ductor cables is analyzed: high temperatures accelerate chemical reactions in insulating materials to change their microstructures as well as their permittivity. The resulting variation of permittivi-ty leads to changes in crosstalk amplitude. Then, experiments are conducted to measure crosstalk amplitudes of cables in a thermal chamber. Finally, based on measured results, time-based varia-tions of crosstalk amplitudes at different temperatures are demonstrated and the equivalent chemical reaction rates calculat-ed. By fitting the rates with the Arrhenius equation, accelerating ratios between different temperatures are obtained.

  • dc.title: Practical Evaluation of Electromagnetic Time Reversal to Locate Partial Discharges on Power Networks in the Presence of Noise dc.contributor.author: Ragusa, Antonella; Sasse, Hugh; Duffy, A. P. dc.description.abstract: The paper proposes an analysis of the performance of a new method to localize Partial Discharges (PDs) on power cables under noisy conditions. The new method is based on the use of the Electromagnetic Time Reversal (EMTR) theory and the ransmission Line Matrix (TLM) numerical method. The investigations have been carried out in a voltage reduced experimental set up, using a RG223 coaxial cable. The effectiveness of the EMTR-based method has been evaluated with different noise levels injected into the cable in order to determine how the method works under noisy conditions. The experimental results have shown that the EMTR method is able to localize PD source with an error that is always less than 1%. Averaging is used over several PD signal recordings at the observation point when the reflected signal is hidden by the noise. dc.description: This work was supported by the European Union’s Horizon 2020 Research and Innovation Programme under the Marie SkÅ‚odowska-Curie Grant under Agreement 838681.

  • dc.title: Application of probabilistic models for multitone electromagnetic immunity analysis dc.contributor.author: Devaraj, Lokesh; Khan, Qazi Mashaal; Ruddle, Alastair R.; Duffy, A. P.; Perdriau, Richard; Koohestani, Mohsen dc.description.abstract: The operational environment of modern electronic systems may include multiple frequency electromagnetic dis- turbances. However, immunity measurements usually employ single frequency continuous waveforms (i.e. single-tones). The performance of two oscillator circuits with different topologies (one simulated and one measured) were used as case studies to in- vestigate immunity to simultaneous single-tone disturbances (i.e. multitones) using probabilistic Bayesian network models. For the multitone analysis, the noisy-OR model was first used to identify the type of causal interactions between simultaneously occurring single-tones. Probabilistic theories derived from the recursive noisy-OR model, which inherits the independence assumptions of the noisy-OR and any known causal dependence between simultaneously occurring single-tones, were then used to predict the probability of higher order multitone failures. For the two case studies, the probability of three-tone failures was estimated using the single-tone and two-tone failure probability values. An improved adaptive recursive noisy-OR model was also proposed to overcome the practical difficulties of obtaining multitone failure probabilities, from either simulations or measurements. dc.description: The research leading to these results has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie SkÅ‚odowska-Curie grant agreement No 812790 (MSCA-ETN PETER). The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.


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Research interests/expertise

  • Validation of computational electromagnetics. The Feature Selective Valdiation (FSV) method is a product of this research.
  • Communications systems physical layer, particularly communications cabling and antennas.
  • Computational electromagnetics.
  • Electromagnetic measurements, particularly involving the reverberation chamber.
  • Technology strategy, particularly forecasting. 

Courses taught

ENGD2009 Electromagnetics
ENGT5254 Electromagnetic Compatibility
ENGD3011 Electronic and mechanical systems
ENGD2021 Product Introduction and Project Management 

Honours and awards

Honorary member of the Romanian EMC (Electromagnetic Compatibility) Society

Membership of external committees

IEEE EMC Society Board of Directors
IEEE EMC Society Standards Education and Training Committee (Chair)
IWCS Board of Directors
BSi TCT7/-/1 member

Membership of professional associations and societies

Fellow of the IET
Senior Member of the IEEE

Professional licences and certificates

Chartered Engineer

Consultancy work

Data comparison and validation
Structured cabling
EMC testing

Current research students

Currently first supervisor to:

Ahmed Aldabbagh
Hassan fadel
Sabir Hussain
Riyadh Mansoor

Second Supervisor to:

Haitham Adarbah
Clive Collins
Bernd Lehmanski
Mohamed Maricar
Andrew Nicholson

Professional esteem indicators

Associate Editor for the IEEE Transactions on EMC
Editor in Chief for the Applied Computational Electromagnetics Society Newsletter
Series Editor for the IET/SciTech Publishing Series on EMC

Alistair Duffy 051216